[PATCH 4.9 30/65] configfs: new object reprsenting tree fragments

From: Al Viro viro@zeniv.linux.org.uk

commit 47320fbe11a6059ae502c9c16b668022fdb4cf76 upstream.

Refcounted, hangs of configfs_dirent, created by operations that add fragments to configfs tree (mkdir and configfs_register_{subsystem,group}). Will be used in the next commit to provide exclusion between fragment removal and ->show/->store calls.

Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Christoph Hellwig hch@lst.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- fs/configfs/configfs_internal.h | 15 ++++- fs/configfs/dir.c | 105 +++++++++++++++++++++++++++++++--------- fs/configfs/file.c | 4 - 3 files changed, 97 insertions(+), 27 deletions(-)

--- a/fs/configfs/configfs_internal.h +++ b/fs/configfs/configfs_internal.h @@ -34,6 +34,15 @@ #include <linux/list.h> #include <linux/spinlock.h>

+struct configfs_fragment { + atomic_t frag_count; + struct rw_semaphore frag_sem; + bool frag_dead; +}; + +void put_fragment(struct configfs_fragment *); +struct configfs_fragment *get_fragment(struct configfs_fragment *); + struct configfs_dirent { atomic_t s_count; int s_dependent_count; @@ -48,6 +57,7 @@ struct configfs_dirent { #ifdef CONFIG_LOCKDEP int s_depth; #endif + struct configfs_fragment *s_frag; };

#define CONFIGFS_ROOT 0x0001 @@ -75,8 +85,8 @@ extern int configfs_create(struct dentry extern int configfs_create_file(struct config_item *, const struct configfs_attribute *); extern int configfs_create_bin_file(struct config_item *, const struct configfs_bin_attribute *); -extern int configfs_make_dirent(struct configfs_dirent *, - struct dentry *, void *, umode_t, int); +extern int configfs_make_dirent(struct configfs_dirent *, struct dentry *, + void *, umode_t, int, struct configfs_fragment *); extern int configfs_dirent_is_ready(struct configfs_dirent *);

extern void configfs_hash_and_remove(struct dentry * dir, const char * name); @@ -151,6 +161,7 @@ static inline void release_configfs_dire { if (!(sd->s_type & CONFIGFS_ROOT)) { kfree(sd->s_iattr); + put_fragment(sd->s_frag); kmem_cache_free(configfs_dir_cachep, sd); } } --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -164,11 +164,38 @@ configfs_adjust_dir_dirent_depth_after_p

#endif /* CONFIG_LOCKDEP */

+static struct configfs_fragment *new_fragment(void) +{ + struct configfs_fragment *p; + + p = kmalloc(sizeof(struct configfs_fragment), GFP_KERNEL); + if (p) { + atomic_set(&p->frag_count, 1); + init_rwsem(&p->frag_sem); + p->frag_dead = false; + } + return p; +} + +void put_fragment(struct configfs_fragment *frag) +{ + if (frag && atomic_dec_and_test(&frag->frag_count)) + kfree(frag); +} + +struct configfs_fragment *get_fragment(struct configfs_fragment *frag) +{ + if (likely(frag)) + atomic_inc(&frag->frag_count); + return frag; +} + /* * Allocates a new configfs_dirent and links it to the parent configfs_dirent */ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *parent_sd, - void *element, int type) + void *element, int type, + struct configfs_fragment *frag) { struct configfs_dirent * sd;

@@ -188,6 +215,7 @@ static struct configfs_dirent *configfs_ kmem_cache_free(configfs_dir_cachep, sd); return ERR_PTR(-ENOENT); } + sd->s_frag = get_fragment(frag); list_add(&sd->s_sibling, &parent_sd->s_children); spin_unlock(&configfs_dirent_lock);

@@ -222,11 +250,11 @@ static int configfs_dirent_exists(struct

int configfs_make_dirent(struct configfs_dirent * parent_sd, struct dentry * dentry, void * element, - umode_t mode, int type) + umode_t mode, int type, struct configfs_fragment *frag) { struct configfs_dirent * sd;

- sd = configfs_new_dirent(parent_sd, element, type); + sd = configfs_new_dirent(parent_sd, element, type, frag); if (IS_ERR(sd)) return PTR_ERR(sd);

@@ -273,7 +301,8 @@ static void init_symlink(struct inode * * until it is validated by configfs_dir_set_ready() */

-static int configfs_create_dir(struct config_item *item, struct dentry *dentry) +static int configfs_create_dir(struct config_item *item, struct dentry *dentry, + struct configfs_fragment *frag) { int error; umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO; @@ -286,7 +315,8 @@ static int configfs_create_dir(struct co return error;

error = configfs_make_dirent(p->d_fsdata, dentry, item, mode, - CONFIGFS_DIR | CONFIGFS_USET_CREATING); + CONFIGFS_DIR | CONFIGFS_USET_CREATING, + frag); if (unlikely(error)) return error;

@@ -351,9 +381,10 @@ int configfs_create_link(struct configfs { int err = 0; umode_t mode = S_IFLNK | S_IRWXUGO; + struct configfs_dirent *p = parent->d_fsdata;

- err = configfs_make_dirent(parent->d_fsdata, dentry, sl, mode, - CONFIGFS_ITEM_LINK); + err = configfs_make_dirent(p, dentry, sl, mode, + CONFIGFS_ITEM_LINK, p->s_frag); if (!err) { err = configfs_create(dentry, mode, init_symlink); if (err) { @@ -612,7 +643,8 @@ static int populate_attrs(struct config_

static int configfs_attach_group(struct config_item *parent_item, struct config_item *item, - struct dentry *dentry); + struct dentry *dentry, + struct configfs_fragment *frag); static void configfs_detach_group(struct config_item *item);

static void detach_groups(struct config_group *group) @@ -660,7 +692,8 @@ static void detach_groups(struct config_ * try using vfs_mkdir. Just a thought. */ static int create_default_group(struct config_group *parent_group, - struct config_group *group) + struct config_group *group, + struct configfs_fragment *frag) { int ret; struct configfs_dirent *sd; @@ -676,7 +709,7 @@ static int create_default_group(struct c d_add(child, NULL);

ret = configfs_attach_group(&parent_group->cg_item, - &group->cg_item, child); + &group->cg_item, child, frag); if (!ret) { sd = child->d_fsdata; sd->s_type |= CONFIGFS_USET_DEFAULT; @@ -690,13 +723,14 @@ static int create_default_group(struct c return ret; }

-static int populate_groups(struct config_group *group) +static int populate_groups(struct config_group *group, + struct configfs_fragment *frag) { struct config_group *new_group; int ret = 0;

list_for_each_entry(new_group, &group->default_groups, group_entry) { - ret = create_default_group(group, new_group); + ret = create_default_group(group, new_group, frag); if (ret) { detach_groups(group); break; @@ -810,11 +844,12 @@ static void link_group(struct config_gro */ static int configfs_attach_item(struct config_item *parent_item, struct config_item *item, - struct dentry *dentry) + struct dentry *dentry, + struct configfs_fragment *frag) { int ret;

- ret = configfs_create_dir(item, dentry); + ret = configfs_create_dir(item, dentry, frag); if (!ret) { ret = populate_attrs(item); if (ret) { @@ -844,12 +879,13 @@ static void configfs_detach_item(struct

static int configfs_attach_group(struct config_item *parent_item, struct config_item *item, - struct dentry *dentry) + struct dentry *dentry, + struct configfs_fragment *frag) { int ret; struct configfs_dirent *sd;

- ret = configfs_attach_item(parent_item, item, dentry); + ret = configfs_attach_item(parent_item, item, dentry, frag); if (!ret) { sd = dentry->d_fsdata; sd->s_type |= CONFIGFS_USET_DIR; @@ -865,7 +901,7 @@ static int configfs_attach_group(struct */ inode_lock_nested(d_inode(dentry), I_MUTEX_CHILD); configfs_adjust_dir_dirent_depth_before_populate(sd); - ret = populate_groups(to_config_group(item)); + ret = populate_groups(to_config_group(item), frag); if (ret) { configfs_detach_item(item); d_inode(dentry)->i_flags |= S_DEAD; @@ -1260,6 +1296,7 @@ static int configfs_mkdir(struct inode * struct configfs_dirent *sd; struct config_item_type *type; struct module *subsys_owner = NULL, *new_item_owner = NULL; + struct configfs_fragment *frag; char *name;

sd = dentry->d_parent->d_fsdata; @@ -1278,6 +1315,12 @@ static int configfs_mkdir(struct inode * goto out; }

+ frag = new_fragment(); + if (!frag) { + ret = -ENOMEM; + goto out; + } + /* Get a working ref for the duration of this function */ parent_item = configfs_get_config_item(dentry->d_parent); type = parent_item->ci_type; @@ -1380,9 +1423,9 @@ static int configfs_mkdir(struct inode * spin_unlock(&configfs_dirent_lock);

if (group) - ret = configfs_attach_group(parent_item, item, dentry); + ret = configfs_attach_group(parent_item, item, dentry, frag); else - ret = configfs_attach_item(parent_item, item, dentry); + ret = configfs_attach_item(parent_item, item, dentry, frag);

spin_lock(&configfs_dirent_lock); sd->s_type &= ~CONFIGFS_USET_IN_MKDIR; @@ -1419,6 +1462,7 @@ out_put: * reference. */ config_item_put(parent_item); + put_fragment(frag);

out: return ret; @@ -1587,7 +1631,7 @@ static int configfs_dir_open(struct inod */ err = -ENOENT; if (configfs_dirent_is_ready(parent_sd)) { - file->private_data = configfs_new_dirent(parent_sd, NULL, 0); + file->private_data = configfs_new_dirent(parent_sd, NULL, 0, NULL); if (IS_ERR(file->private_data)) err = PTR_ERR(file->private_data); else @@ -1743,8 +1787,13 @@ int configfs_register_group(struct confi { struct configfs_subsystem *subsys = parent_group->cg_subsys; struct dentry *parent; + struct configfs_fragment *frag; int ret;

+ frag = new_fragment(); + if (!frag) + return -ENOMEM; + mutex_lock(&subsys->su_mutex); link_group(parent_group, group); mutex_unlock(&subsys->su_mutex); @@ -1752,7 +1801,7 @@ int configfs_register_group(struct confi parent = parent_group->cg_item.ci_dentry;

inode_lock_nested(d_inode(parent), I_MUTEX_PARENT); - ret = create_default_group(parent_group, group); + ret = create_default_group(parent_group, group, frag); if (ret) goto err_out;

@@ -1760,12 +1809,14 @@ int configfs_register_group(struct confi configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata); spin_unlock(&configfs_dirent_lock); inode_unlock(d_inode(parent)); + put_fragment(frag); return 0; err_out: inode_unlock(d_inode(parent)); mutex_lock(&subsys->su_mutex); unlink_group(group); mutex_unlock(&subsys->su_mutex); + put_fragment(frag); return ret; } EXPORT_SYMBOL(configfs_register_group); @@ -1852,10 +1903,17 @@ int configfs_register_subsystem(struct c struct dentry *dentry; struct dentry *root; struct configfs_dirent *sd; + struct configfs_fragment *frag; + + frag = new_fragment(); + if (!frag) + return -ENOMEM;

root = configfs_pin_fs(); - if (IS_ERR(root)) + if (IS_ERR(root)) { + put_fragment(frag); return PTR_ERR(root); + }

if (!group->cg_item.ci_name) group->cg_item.ci_name = group->cg_item.ci_namebuf; @@ -1871,7 +1929,7 @@ int configfs_register_subsystem(struct c d_add(dentry, NULL);

err = configfs_attach_group(sd->s_element, &group->cg_item, - dentry); + dentry, frag); if (err) { BUG_ON(d_inode(dentry)); d_drop(dentry); @@ -1889,6 +1947,7 @@ int configfs_register_subsystem(struct c unlink_group(group); configfs_release_fs(); } + put_fragment(frag);

return err; } --- a/fs/configfs/file.c +++ b/fs/configfs/file.c @@ -502,7 +502,7 @@ int configfs_create_file(struct config_i

inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL); error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, - CONFIGFS_ITEM_ATTR); + CONFIGFS_ITEM_ATTR, parent_sd->s_frag); inode_unlock(d_inode(dir));

return error; @@ -524,7 +524,7 @@ int configfs_create_bin_file(struct conf

inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL); error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode, - CONFIGFS_ITEM_BIN_ATTR); + CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag); inode_unlock(dir->d_inode);

return error;